The present application relates generally to apparatus and assemblies concerning the design and operation of rotor blades in turbine engines. More specifically, but not by way of limitation, the present application relates to configurations of cooling channels within turbine rotor blades.
As provided below, the invention of the present application is described in relation to exemplary applications within the turbine section of a combustion turbine engine. It will be appreciated by those of ordinary skill in the art that the present invention may also be used in other types of combustion turbines, such as those used in commercial aircraft.
It will be appreciated that combustion turbine engines generally include a compressor, combustor, and turbine sections. The compressor and turbine sections generally include rows of blades that are axially stacked in stages. Each stage includes a row of circumferentially-spaced stator blades, which are fixed, and a row of rotor blades, which rotate about a central turbine axis or shaft. In operation, generally, the compressor rotor blades rotate about the shaft, and, acting in concert with the stator blades, compress a flow of air. The supply of compressed air then is used in the combustor to combust a supply of fuel. The resulting flow of hot expanding gases from this combustion, i.e., the working fluid, is expanded through the turbine section of the engine. The flow of working fluid through the turbine induces the rotor blades to rotate. The rotor blades are connected to a central shaft such that the rotation of the rotor blades rotates the shaft. In this manner, the energy contained in the fuel is converted into the mechanical energy of the rotating shaft, which, for example, may be used to rotate the rotor blades of the compressor, such that the supply of compressed air needed for combustion is produced, and the coils of a generator, such that electrical power is generated.
During operation, because of the extreme temperatures of the hot-gas path, the velocity of the working fluid, and the rotational velocity of the engine, turbine blades, which, as described, generally include both the rotating rotor blades and the fixed, circumferentially-spaced stator blades, become highly stressed with extreme mechanical and thermal loads.
The ever-increasing demand for energy makes the objective of engineering more efficient combustion turbine engines an ongoing and significant one. While several strategies for increasing the efficiency of turbine engines are known, it remains a challenging objective because these alternatives—which, for example, include increasing the size of the engine, increasing the temperatures through the hot-gas path, and increasing the rotational velocities of the rotor blades—generally place additional strain on parts that are already highly stressed. As a result, improved apparatus and assemblies that mitigate the operational stresses placed on turbine blades are in great demand.
As one of ordinary skill in the art will appreciate, one strategy for alleviating the thermal stress on the blades is through active cooling during operation, which may allow the blades to withstand higher firing temperatures, withstand greater mechanical stresses at high operating temperatures, and/or extend the life of the blades, all of which may allow the turbine engine to be more cost-effective and efficient in its operation. One way to cool blades during operation is through the use of internal cooling passageways or circuits. Generally, this involves passing a relatively cool supply of compressed air, which may be supplied by the compressor of the turbine engine, through internal cooling channels within the blades. As the compressed air passes through the blade, it convectively cools the blade, which allows the part to withstand firing temperatures that it otherwise could not.
For a number of reasons, it will be appreciated that great care is required in designing and manufacturing the configuration of these cooling channels. First, the use of cooling air comes at a price. That is, air that is diverted from the compressor to the turbine section of the engine for cooling bypasses the combustor and, thus, decreases the efficiency of the engine. As such, cooling passages must be designed to use air in a highly effective manner, i.e., provide the necessary coverage and cooling efficiency, so that a minimum amount of air is needed for this purpose. Second, to reduce mechanical loads, cooling passages should be formed to remove unnecessary weight from the blade; however, the blades still must remain strong to withstand the large mechanical loads. Cooling channels, therefore, must be designed such that the turbine blade has a lightweight but strong construction, while stress concentrations that would negatively affect the blades resilience are avoided. In short, what is needed is a turbine blade cooling configuration that performs well in more aggressively shaped, thinner aerodynamic blade configurations, promotes lighter blade internal construction, maintains the structural support of the turbine blade, and delivers high cooling effectiveness.